Free tool
Port Checker
Test whether a port on any IP or hostname is reachable from the internet. Verify port forwarding, firewall rules, and server accessibility.
Common ports
Checks are made from our server. Leave host blank to test your own IP automatically.
How it works
Understanding ports and port forwarding
What port forwarding is
Port forwarding tells your router to send incoming traffic on a specific port to a device on your local network. Without it, your router blocks all unsolicited inbound connections.
Why 'open' means reachable
When this tool shows a port as open, it means our server successfully established a TCP connection to the target on that port. Any device on the internet can reach that port.
Why ports show as closed
A closed or filtered result means the connection timed out or was refused. Common causes: port forwarding not configured, firewall blocking the port, or your ISP blocking inbound traffic on that port.
ISP port blocking
Many ISPs block inbound traffic on well-known ports (80, 443, 25) on residential connections. If you can't open these ports, switch to an alternative port or use a reverse proxy.
Reference
Common ports for home servers
| Port | Protocol / Service | Notes |
|---|---|---|
| 80 | HTTP | Plain web traffic. ISPs often block inbound 80 on residential lines. |
| 443 | HTTPS | Encrypted web traffic. Required for SSL certificates and modern browsers. |
| 22 | SSH | Remote shell access. Consider moving to a non-standard port to reduce bot traffic. |
| 21 | FTP | File transfer. Use SFTP (port 22) instead for encrypted transfers. |
| 8080 | HTTP-Alt | Common alternative when ISPs block port 80. Used by many web apps. |
| 8443 | HTTPS-Alt | Alternative HTTPS port when 443 is blocked. |
| 3389 | RDP | Windows Remote Desktop. Heavily targeted by brute-force bots. |
| 25565 | Minecraft | Java Edition game server default. Bedrock uses UDP 19132. |
| 32400 | Plex | Plex Media Server. Can use relay without open port, but direct is faster. |
| 554 | RTSP | Real Time Streaming Protocol. Used by IP cameras and NVRs for live video feeds. |
| 51820 | WireGuard | WireGuard VPN (UDP). Lets you tunnel into your home network. |
Port open? Now keep the hostname stable.
Port forwarding only works if your IP stays the same — or your hostname tracks it. NovaDNS does that automatically.